Coronary artery disease is commonly treated by relatively non-invasive techniques such as percutaneous translumenal coronary angioplasty (PTCA). Conventional PTCA is well known in the art and typically involves the use of a balloon catheter, possibly in combination with other intravascular devices such as a guide wire and a guide catheter. A typical balloon catheter has an elongate shaft with a balloon attached to its distal end and a manifold attached to its proximal end. In use, the balloon catheter is advanced into a guide catheter and over a guide wire such that the balloon is positioned adjacent a restriction in a diseased coronary artery. The balloon is then inflated and the restriction in the vessel is opened.
A common problem with PTCA is the occurrence of restenosis in approximately one-third to one-half of the patients treated, depending on the condition of the vessel being treated. Various therapies have been proposed to treat restenosis. For example, some types of light have been suggested as a means to prevent restenosis of a previously dilated vascular restriction. U.S. Pat. No. 5,417,653 to Sahota et al. discloses a method of preventing restenosis by delivering light utilizing a balloon catheter. The balloon described in Sahota '653 serves both to dilate the stenosis and to displace blood from the treatment site. Since blood is relatively opaque to UV light, displacing blood from the treatment site is important for treating the vascular wall with UV light. A significant problem with the method described in Sahota '653 is that blood becomes trapped between the outside surface of the inflated balloon and the inside surface of the vascular wall. Since blood is relatively opaque to UV light, the trapped blood prevents effective treatment of the vascular site.
Utilizing a "weeping balloon" as described in U.S. Pat. No. 5,087,244 to Wolinsky has been suggested as a method of eliminating the blood trapped between the outside surface of the inflated balloon and the inside surface of the vascular wall. However, this system does not allow the balloon to be inflated independently of infusing fluid around the balloon. This is a significant disadvantage because it is not considered desirable to infuse at the relatively higher balloon inflation pressure. Infusing at such a high pressure may result in excessive infusion flow rates, damage to the vessel wall and/or life threatening dissections. In addition, the balloon diameter cannot be controlled independently of the infusion rate if a compliant balloon is used.